Japanese Unexamined Patent Application Publication 2009-31003 (“JP '003”), below, discloses a dual pressure sensor for detecting pressures, of that which is to be measured, with each of two pressure sensors. The dual pressure sensor as set forth in JP '003 can be installed in, for example, a valve unit of a flow control valve as set forth in Japanese Unexamined Patent Application Publication 2009-115302 (“JP '302”), below. In this case, the dual pressure sensor detects both the fluid pressures on the upstream side of the valve unit and on the downstream side of the valve unit, and outputs to a flow measuring device for controlling the flow control valve. The flow measuring device calculates the flow of the fluid flowing within a flow path of the flow controlling valve based on the differential pressure between the fluid pressure on the upstream side and the fluid pressure on the downstream side.
Note that this pressure sensor has a temperature characteristic wherein the output value will fluctuate with the temperature at the time of use. In order to calculate the flow of the fluid accurately when using a pressure sensor having this type of temperature characteristic, it is necessary to perform accurate temperature correction on the output value of the pressure sensor to eliminate from the output value the fluctuation portion due to temperature variation. Japanese Unexamined Patent Application Publication 2004-294110, below, discloses a technology wherein, when correcting the sensor output value for temperature, the temperature range in a non-linear temperature characteristic curve is divided into a plurality of segments, and a temperature correction is performed using the values on the lines that connect the ends of each of the segments. Japanese Unexamined Patent Application Publication H6-294664, below, discloses a technology wherein a high-order equation that most nearly approximates the temperature characteristic curve is calculated, and temperature correction of the output value of the sensor is performed using the high-order equation.
In the temperature correction in JP '003, a correction is possible in a state wherein there is no difference between the temperature characteristic curves at both ends of the divided segments that are connected by straight lines, but if there is a large difference between the temperature characteristic curves at the intermediate positions in the divided segments, the accuracy of the temperature correction will fall. Moreover, in the temperature correction in JP '302, described above, because a single high-order correcting equation is made, is not possible to correct with excellent accuracy the entire scope of temperatures, causing the difference from the temperature characteristic curve to be large, depending on the temperature band wherein the correction is being made, resulting in a decrease in accuracy of the temperature correction.
Given this, the object of the present invention is to provide a physical quantity sensor wherein the accuracy of the temperature correction can be improved.